1. Field of the Invention
The present invention relates to a velocity calculation device, a velocity calculation method, and a navigation device suitably applied, for example, to a portable navigation device.
2. Description of Related Art
A navigation device in the related art is configured to receive positioning signals (hereinafter, referred to also as GPS signals) from a plurality of GPS (Global Positioning System) satellites and to calculate a current position of the vehicle on the basis of the GPS signals.
The navigation device as above, however, fails to receive GPS signals from the GPS satellites when the vehicle on which is mounted the navigation device goes, for example, into a tunnel or an underground parking and thereby becomes unable to calculate a current position of the vehicle on the basis of the GPS signals.
To avoid such an inconvenience, there is a type of navigation device configured to calculate a velocity in the travel direction on the basis of the acceleration in the horizontal direction orthogonal to the travel direction of the vehicle and an angular velocity about the vertical axis orthogonal to the travel direction at the time of cornering, and to calculate a current position on the basis of the velocity in the travel direction even in a case where the navigation device fails to receive the GPS signals. An example of such a navigation device is disclosed in JP-A-2008-76389.